In gas and steam power stations, gas and steam turbines are available as types of drive. Gas and steam turbines are continuous flow machines. As a result of its short start-up time, a gas and steam power station can provide high power levels in a short time. The combination of gas turbines and steam turbines produces electrical power with good efficiency and high flexibility using various primary energy sources, and in terms of the operational characteristics of the entire turbine set.
The gas circuit and steam circuit are connected in one system, in order to increase the efficiency. The hot exhaust gas from the gas turbine is used to produce steam in a waste-heat boiler, and this produces mechanical torque in the steam turbine (three-pressure process). This combination increases the efficiency for the production of electrical power by about 36% to, for example, 57(%). One such installation is illustrated by way of example in FIG. 1 (outline sketch of a single-shaft gas and steam installation with an SSS clutch between the steam turbine and the synchronous generator). The example of a gas and steam single-shaft installation has a gas turbine 1, a generator 2, an exciter 3, a clutch 4 and a steam turbine 5.
In the case of the single-shaft installation considered by way of example in FIG. 1, the gas turbine and steam turbine are located with just one generator on a common shaft train. Approximately 10% of the investment costs can be saved by the lack of a second generator and its associated components.
In order to allow the advantages of the gas turbine to be exploited as well as possible, the steam turbine is first of all disconnected from the shaft train. At the operating temperature, the steam turbine can be engaged, virtually independently of the load state of the generator, via a clutch, for example via a synchronizing, self-selecting, over-running tooth-type clutch (SSS clutch).
The system comprising the gas turbine and generator in this case has a synchronous rotation speed. When the steam turbine exceeds this rotation speed, it is automatically engaged via a screw thread and can then transmit power to the electrical generator. The overall power of the turbine set is split such that approximately two thirds is provided by the gas turbine and one third by the steam turbine.
During steady-state, engaged power operation, the measured shafts and bearing oscillation are dependent on the relative angular position of the partial shaft trains with respect to one another, irrespective of whether these are machines which are operated at 50 Hz or 60 Hz. In this case, the maximum permissible limit values for bearing oscillation and shaft oscillation are exceeded at certain angular positions.
Measurements of the bending oscillations upstream and downstream of the clutch and of the associated clutch angle can be used as a basis for identification of good and bad positions.